Uhm... okay..
All Levels:
FF pretty much summed it up. Non-deaf rings, no thok barrier, obviously placed invincibility and super sneaker TVs, large empty spaces, small pathways...
And for hell's sake, please turn off the SA Mode! I don't like having to use the console command ANALOG OFF each time a level starts.
Zone 1:
Very long hallways, obviously placed item boxes, you get the drill. Levels are pretty short. Why is spikeball Eggman used as the boss?
Zone 2:
Death pits. Way too many death pits for just the second zone. And the second act was just some crappy invisible maze of glitchiness. The boss level for this zone has GOT to go.
Zone 3:
Still pretty meh. At least in this zone you showed off your knowledge of waterblocks. Boss for this zone is glitched up for some reason. Slime isn't scattering, and the pogo at the end is all messed up.
Zone 4:
You've definitely showed improvement in this level, I'll admit. Thok barrier, decent looking platforms (used wrong texture though. Shouldn't be cracked looking), etc.. But what's with the bosses? You don't really need to defeat them. This zone was also very short.
Conclusion:
Judging by Zone 4, you have gained more knowledge about level making, and as such, it would be a good idea to redo the rest of your pack with higher standards.
Things to work on:
Length - All the levels are rather short. Levels should be large and immersive, with many different paths, and secrets for you to find.
Detail - The open areas are rather lack-luster. Try putting more objects in these places, to make them more explorable. GFZ2 is a pretty good level to use as a reference. MR is probably better, though.
Item Placement - You've somewhat improved on this in later levels, but again, you should use your new standards on all of your levels. Remember, it's a bad idea to place lots and lots of enemies in one area.
Others - Work the thok barrier into all levels. There really is no excuse for a level not to have a thok barrier. Also, you should probably turn off SA Mode.
Judging by these facts, this is probably your first set of levels. I'll go easy on you. However, you, in return, must research how to make deep, enjoyable levels.